Coronary angiography allows for excellent visualization of coronary arteries. However, assessment of functional stenosis severity is limited. Fractional flow reserve, FFR, is a reliable measure for grading stenosis. Based on the aortic pressure Pa and the pressure Pd distal to the stenosis, FFR is defined as: FFR=Pd/Pa.
FFR is a widely used index to assess the functional impact of a stenosis in the coronary arteries. Typically, FFR is measured in an invasive fashion, by advancing a pressure wire past the stenosis and measuring the pressure drop across the stenosis. In recent years, non-invasive determination of FFR has been pursued, using fluid-dynamics simulations of blood flow based on CT angiography images.